ON THE RELATION BETWEEN THE CONFIGURATION OF ACTION POTENTIAL AND THE CONTRACTION OF URETER

Abstract

By recording the electrogram and mechanogram of the ureter simultaneously, the relationship between the configuration of action potential and contraction was studied.The action potential of the guinea pig's ureter consists of two components, the slow potential and the oscillating spike potential. Tetraethylam-monium (TEA) ion diminished the spike component without affecting the slow component. In this case, the slow potentials appeared repetitively and spontaneously, each of them was accompanied by contraction and the evident summation of contraction could be observed. The contraction of TEA-ureter was of tetanic nature.When NaCl in Krebs solution was substituted by choline chloride, the action potential lost its slow component and there occurred the repetitive burst of grouped spike potentials. The single spike potential evoked the single weak contraction. In each burst, the summation of contraction was recorded. The contraction of choline-ureter was also of tetanic nature.The effect of oxytocin upon the ureter was similar to that of Ca ion deficient environment. By the administration of oxytocin in the soaking fluid, the action potential lost its spike component but the slow component remained unaffected. In this case, however, with the decrease in size of the spike potential, the contraction became weaker and finally disappeared. The disappearance of contraction by oxytocin is due to the disturbance or block of the excitation-contraction coupling.From the facts mentioned above, it could be concluded that both slow and spike components in action potential of the guinea pig's ureter held the ability to evoke the contraction, as far as the excitation-contraction coupling was not disturbed.